Field
The present application relates to methods for classifying articles, in particular for classifying particles comprising magnetocalorically active material, and methods for fabricating a magnetocalorically active working component for magnetic heat exchange.
Description of Related Art
The magnetocaloric effect describes the adiabatic conversion of a magnetically induced entropy change to the evolution or absorption of heat. Therefore, by applying a magnetic field to a magnetocaloric material, an entropy change can be induced which results in the evolution or absorption of heat. This effect is harnessed in magnetic heat exchangers to provide refrigeration and/or heating.
Materials such as Gd5(Si5Ge)4, Mn(As,Sb) and MnFe(P5,As) have been developed which have a magnetic transition temperature, or Curie Temperature, at or near room temperature. The magnetic transition temperature translates to the operating temperature of the material in a magnetic heat exchange system. Consequently, these materials are suitable for use in applications such as building climate control, domestic and industrial refrigerators and freezers as well as automotive climate control.
Magnetic heat exchange technology is of interest as magnetic heat exchangers are, in principle, more energy efficient than gas compression/expansion cycle systems. Furthermore, magnetic heat exchangers are environmentally friendly as ozone depleting chemicals such as CFCs are not used.
WO 2009/090442 discloses a composite article which includes a plurality of layers, each comprising magnetocalorically active material. Each layer has a different magnetic transition temperature and the layers are arranged such that the magnetic transition temperature increases from one end of the composite article to the other to provide a layered working component for magnetic heat exchange. This layered arrangement of increasing or decreasing magnetic transition temperatures enables the operating range of the working component to be increased compared to a working component which includes magnetocalorically active material having a single magnetic transition temperature.
In order to manufacture such a layered working component, a plurality of magnetocalorically active materials in the form of powders may be used. Each magnetocalorically active material has a different Curie temperature. Therefore, methods for manufacturing a plurality of magnetocalorically active materials of differing magnetic transition temperature are desirable.